Luer Access Valves (LAV), often referred to as Needless Injection Sites (NIS), are intended to be compliant with the ISO luer thread standard (ISO 594-2), but vary dimensionally, even within the standard. The ISO standard does not anticipate mating caps which lack a luer post—such as disinfecting caps. The problem is providing a secure fit which will not become loose with time and use. In a standard luer connection, the securement is provided by the locking taper fit of the male luer post in the female luer. In a disinfecting cap for an NIS, there is no luer post, and the securement must be provided by other features. In the design presented herein, the securement is provided by a compression fit of the inner diameter of the cap, and the major thread diameter of the NIS, as discussed in more detail below.